Conventional power drills typically have a driven member including a three jaw chuck which grips a working element such as a drill bit or screw driver head or the like. The chuck jaws are adjustable, normally by rotating an adjustment nut relative to the chuck body. In some case, the nut is rotated using a key, in other cases the user supplies a resistance force by gripping the nut while power is supplied to rotate the chuck body. More recently the applicant has designed a power drill having a locking sleeve that selectively engages the nut to provide the resistance force.
The locking sleeve has been found to be particularly effective in resisting the force produced by the drive means to grip the working element in the chuck jaws. However, the applicant has appreciated that if too much force is applied to the jaws it may damage or even crush the working element or break the jaws.
The above discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed in Australia before the priority date of this application.
It is an object of this invention to provide a power tool that is convenient to use. It is a further object of the invention to provide a power tool having means to drive gripping jaws of the driven member to efficiently and safely grip a working element. It is a further object of this invention to provide a power tool that allows the user to control the torque supplied to the gripping jaws to protect elements of the power tool and the working element.